The paper describes the current status of knowledge of the viscosity of refrigerants R32, R124, R125, R134a, R141b and R152a and their mixtures, in the liquid and vapour states along the saturation line and as a function of pressure. The analysis reveals that there remain significant discrepancies between the results of measurements of the viscosity of pure refrigerants by different authors. These differences are particularly marked when different techniques are employed but almost always exceed the claimed mutual uncertainties. The theoretically-based scheme of Vesovic and Wakeham (VW) for the prediction of the viscosity of mixtures from their pure components is used in a modified form to examine predictions of the behaviour of refrigerant mixtures. (C) 2003 Elsevier B.V. All rights reserved.